From Consumer Wiki
The California Public Utilities Commission (CPUC) has regulatory and safety oversight over railroads, light rail transit agencies, rail crossings, moving companies and for-hire passenger carriers (limousines, airport shuttles, charter and scheduled bus operators). The CPUC issues permits to airport shuttles in order to carry passengers.
California Public Utilities Commission
Complaint Intake Unit - Transportation Enforcement Section
505 Van Ness Avenue
San Francisco, CA 94102-3298
Email - firstname.lastname@example.org
CPUC complaint form: